Seal for a pneumatic servo motor



Nov. 4, 1958 E}. E. HUPP SEAL FOR A PNEUMATIC SERVO MOTOR Filed Feb. 6, 1956 A H I V M N fi IMH mH m WE @A D M W w EM United States Patent 2,859,055 SEAL FOR A PNEUMATIC SERVO MOTOR Edward E. Hupp, South Bend, Ind., assignor to Bendix Aviation Corporation, South Bend, Iud., a corporation of Delaware Application February 6, 1956, Serial No. 563,589

3 Claims. (Cl. 28615) The present invention relates to servomotors of the type having an internal piston provided with a force transmitting member which extends through a wall of the servo-motor, and more particularly to a type of pneumatic seal adaptable for use with such structures and which will accommodate relative lateral movement of the structures between which it extends.

An object of the present invention is the provision of a servo-motor of the above described type having new and improved pneumatic sealing means between its force transmitting member and the housing of the servo-motor which will accommodate lateral movement between the force transmitting member and the housing of the servomotor.

Another object of the present invention is the provision of a new and improved pneumatic seal for a shaft adapted to move in and out with respect to another member and comprising an O-ring positioned about such shaft, a sealing washer extending about the shaft and positionedbetween the O-ring and said other member, and means biasing the O-ring against the sealing washer to cause said sealing washer to abut said other member.

The invention resides in certain constructions and combinations and arrangement of parts and further objects and advantages will be apparent to those skilled in the art to which the invention relates from the following description of the preferred embodiment described with reference to the accompanying drawing forming a part of this specification, in which:

Figure 1 is a longitudinal cross-sectional view of a pneumatic servo-motor embodying the principles of thepresent invention; and

Figure 2 is a fragmentary cross-sectional view of the new and improved pneumatic sealing means utilized in the pneumatic servo-motor shown in Figure 1.

Referring to the drawing, there is shown a servo-motor A having an enclosed cylinder 18 provided with an internal piston 12 which in turn carries a force transmitting member or tubular shaft 14 which extends through openings 16 and 18 in the end wall 20 and spacermember 22, respectively, of the servo-motor. The outer end of the force transmitting member 14 is provide with a U- shaped abutment surface 24 adapted to receive the abutment pin 26 affixed to one end of a reaction linkage 28. The reaction linkage 28 is pivotally supported at a point spaced apart from the abutment pin 26, such that movement of the piston 12 causes the abutment pin 26 to move in an arcuate path. Because the U-shaped abutment surface 24 engages the top and bottom portions of the pin 26, arcuate movement of the pin 26 imparts some lateral motion to the force transmitting member 14 as it is moved through the openings 16 and 13 by the piston 12. For a more complete description of the construction and operation of the servo-motor shown in the drawing, reference may be had to the previously filed Edward E. Hupp et a1 application entitled, Pneumatic Servo-Motor Construction.

The servo-motor shown in the drawing employs a new 2,859,055. Patented N 0v; 4, 1958 and improved pneumatic seal between its force transmittmg member 14 and the end wall 20 to prevent the atmosphere from entering the partially evacuated cylinder chamber 30 during actuation of the servo-motor. The pneumatic sealing structure shown in the drawing generally comprises an O-ring 34 positioned about the forcetransmitting member 14 and positioned externally of the end wall 20 of the cylinder 10. The O-ring 34 preferably has a normal internal diameter slightly less than the out side diameter of member 14, such that it tightly engages member 14 when placed about it. A comparatively rigid sealing washer 36 having a smooth surface and preferably made from non-metallic material which will not score member 14, as for example, nylon or Spauldite (fabric impregnated with a phenolic resin) is positioned about the shaft 14 between the end wall 20 and the O-ring 34. The external face of the end wall 20 is provided with a facing of a smooth semi-resilient material as, for example, rubber, to provide sealing engagement with the sealing washer 36. An annular generally cup-shaped retaining ring 40 having a centrally located opening slightly larger than shaft 14 is positioned about the shaft 14 outwardly from the O-ring 34 with its horizontal leg portions engaging the radially outer surface of the sealing washer 36. The annular retaining ring 40 is biased against the O-ring 34 by a coil spring 42 positioned between the annular retaining ring 40 and the spacer member 22. The radially outer portion of the bottom of the cupshaped retaining ring 40 is preferably deformed inwardly to form an abutment or reference surface 46 spaced from the portion which abuts the O-ring 34 a distance which is slightly less than the normal thickness of O-ring 34 to provide a predetermined deformation of the O-ring 34. Force from the coil spring 42 forces the reference surface 46 of the retaining ring 40 against the sealing washer 36, to in turn force the sealing washer 36 against the facing 38 and effect a seal therewith. At the same time, the retaining ring 40 forces the O-ring 34 against the sealing washer 36 to effect a seal therewith. In order that angular movement of the force transmitting member 14 can be accommodated by the sealing structure, it is necessary that the total longitudinal thickness of the structure be as short as possible. In the sealing structure of the preferred embodiment, the sealing washer 36 will be made quite thin, and the central opening of the retaining ring 40 will be made large enough such that the retaining ring 40 will not contact the force transmitting member 14 at any time.

During operation of the servo-motor A, the force transmitting member or tubular shaft 14 is moved laterally with respect to the end wall 20, as previously described. Lateral movement of the shaft 14 is transmitted to the sealing washer 36, causing the sealing washer 36 to slide laterally over the external surface of the facing material 38. The spring 42 is adapted to both accommodate this movement and hold the sealing washer 36 in engagement with the facing material 38 to maintain a seal therewith throughout the lateral movement. In the embodiment shown in the drawing, the horizontal leg of the retaining washer 40 engages the peripheral surface of the sealing washer 36 such that the lateral movement of the shaft 14 is transmitted to the sealing washer 36 which in turn carries the retaining washer 40 with it.

While the preferred embodiment has been described as utilizing a semi-resilient material, that is, rubber, for the facing 38 and a non-metallic comparatively rigid material for sealing washer 36, it will be apparent that one or the other of the engaging surfaces of these membersmight be made of a metallic material, provided it were manufactured with sufficient close tolerances to provide an essentially fiat surface. It might also be acceptable in some instances to omit the facing 38, utilize a metallic sealing washer 36, and to lap the sealing-washer 36 into sealing engagement with the outer surface of the end wall 20. i

It will be seen that the objects and advantages enumerated, as well as others, have been achieved, and that there is provided a new and improved type of pneumatic seal which will accommodate lateral movement between members which are reciprocated relative to each other.

While the preferred embodiment of the invention has been described in considerable detail, I do not wish to be limited to the particular construction shown which may be varied within the scope of the invention and it is the intention to cover hereby all adaptations, modifications and arrangements thereof, which come within the prac tice of those skilled in the art to which the invention relates.

I claim:

1. In a fluid pressure seal adapted to accommodate angular and lateral movement: a first member having a flat sealing surface with an opening therein; a second member extending through said opening, said opening in said first member being large enough to accommodate lateral and angular movement of said second member; a generally rigid disc shaped member having a hole therein through which said second member extends positioned about said second member in sealing abutment with said flat sealing surface, a ring of elastic material in abutment with said disc shaped member and tightly engaging the surface of said second member, said disc shaped member being made from a non-galling material and its hole being constructed to accommodate angular movement of said second member without said hole being large enough to permit extrusion of said ring into said hole, a retainer member having an opening therein through which said second member extends positioned about said second member against said ring, the opening in said retainer member being constructed to accommodate the angular movement of said second member, and means biasing said retainer member toward said surface of said first member, whereby angular movement of the second member relative to the seal produces a pivotal action with respect to said disc shaped member.

2. In a fluid pressure seal adapted to accommodate angular and lateral movement: a first member having a fiat sealing surface with an opening therein; a second member extending through said opening, said opening in said first member being large enough to accommodate lateral and angular movement of said second member; a generally rigid and relatively thin disc shaped member having a hole therein through which said second member extends positioned about said second member in sealing abutment with said flat sealing surface, a ring packing of elastic material in abutment with said disc shaped member and tightly engaging the surface of said second member, said disc shaped member being made from a non-galling material and being sufficiently thin to enable its hole to accommodate angular movement of said second member without said hole being large enough to permit extrusion of said ring into said hole, a retainer member having an opening therein through which said second member extends positioned about said second member against said ring, said retainer member being laterally secured to said disc shaped member and the opening in said retainer member being large enough to accommodate the angular movement of said second memher when said second member engages the side walls of the opening in said disc shaped member and pivots with respect thereto, and means biasing said retainer member toward said surface of said first member, whereby angular movement of the second member relative to the seal produces a pivotal action with respect to said disc shaped member, and the angular movement on either side of the disc shaped member is accommodated by the openings in said first and retainer members respectively.

3. In a fluid pressure seal between reciprocatory members adapted to accommodate angular and lateral movement: a first member having a flat sealing surface with an opening therein; a reciprocable member extending through said opening, said opening in said first member being large enough to accommodate lateral and angular movement of said reciprocable member; a generally rigid disc shaped member having a hole therein through which said reciprocable member extends positioned about said reciprocable member in sealing abutment with said flat sealing surface, a ring of elastic material in abutment with said disc shaped member and tightly engaging the surface of said reciprocable member, said disc shaped member being made from a non-galling material and its hole being constructed to accommodate angular movement of said reciprocable member without said hole being large enough to permit extrusion of said ring into said hole, a stamped sheet metal disc having an opening therein through which said reciprocable member extends positioned about said reciprocable member against said ring and having a bent outer peripheral portion which extends over and confines the outer peripheral portion of said non-galling disc shaped member, the opening in said sheet metal disc being constructed to accommodate pivotal movement of said reciprocable member with respect to said non-galling disc shaped member, and means biasing said sheet metal disc toward said surface of said first member, whereby angular movement of the reciprocable member relative to the seal produces a pivotal action with respect to said disc shaped member and lateral movement of said reciprocable member about said non-galling disc shaped member to carry the sheet metal disc laterally therewith and prevent its galling of said reciprocable member.

References Cited in the file of this patent UNITED STATES PATENTS 2,575,549 Doble Nov. 20, 1951 2,639,928 Robbins May 26, 1953 2,687,908 Vorech Aug. 31, 1954 2,728,592 Vorech Dec. 27, 1955 

